Ensure everything still works if RR is included before the test framework

Also a bit of refactoring of the autohook stuff
Remove the adapter shims for Rspec and RSpec

People who use RR along with RSpec will most likely be using
`RSpec.configuration.mock_with(:rr)` instead of including an RR adapter mixin
into their test case as MiniTest or Test::Unit people are used to doing, so
there is no need to shim this. In the case of
RR::Adapters::Rspec::InvocationMatcher, we will handle this in a later commit.
Split off new adapters into a separate namespace (Integrations)

This way we don't have to rename MiniTest to MiniTest4. This also makes it so
that people who were supplying a custom adapter for RSpec-2 (via
RR::Adapters::RSpec2) can continue to do so without it conflicting with our
stuff.
Bump to 1.1.0.rc2